An image duplicating apparatus is known in which the document to be duplicated is scanned by the movable units of the optical system driven for movement with respect to the document which is fixedly held in place. This mode of scanning a document in an image duplicating apparatus is herein referred to as scanner-moved scanning mode. Also known is an image duplicating apparatus in which the document to be duplicating is scanned by the optical system while the document is being moved with respect to the optical system which fixedly held in place. This mode of scanning a document in an image duplicating apparatus is herein referred to as document-moved scanning mode. The present invention is concerned with an image duplicating apparatus which has both the scanner-moved scanning mode and the document-moved scanning mode and which allows the user to select either of the two different scanning modes.
The document-moved scanning mode is advantageous over the scanner-moved scanning mode in that the period of time required for the duplication of especially a large number of documents since there is no period of time required for the movement of the optical scanner units and the plurality of documents can be duplicated successively. In the document-moved scanning mode, a document is scanned while the document is being conveyed on the document support table by means of an endless drive belt. Due to the sliding friction thus produced between the document and the document support table, the endless belt tends to slide on the document sliding on the table. This results in an irregularity in the speed of movement of the document on the table and may thus cause a failure in achieving strict synchronism between the scanning speed and the speeds at which various active units and members of the apparatus are to operate. Such active units and members include the photosensitive drum and the rollers for feeding print sheets to the drum. The document-moved scanning mode is in this respect lower in performance reliability than the scanner-moved scanning mode.
On the other hand, when a document is to be duplicated to a reduced or magnified scale in the document-moved scanning mode, it is required that the speed at which the document transport belt be controlled to vary in accordance with the desired reduction or magnification ratio. Intricate techniques and control devices, which are usually low in reliability, are however necessitated for this purpose and, accordingly, it is ordinarily not desirable to vary the reduction/magnification ratio during document-moved scanning mode of operation.
The scanner-moved mode of scanning is thus more reliable in performance and more adapted for controlling the reduction/magnification ratio than the document-moved mode of scanning but has a problem when it is desired that a plurality of sets of printed outputs are to be produced each from a plurality of documents and assorted each in a sequence identical to that of the documents where a page sortor unit is not available. When such a page sorting mode is selected for collecting printed outputs, the apparatus is required to repeat cycles of operation each for feeding a document to the document support table, correctly positioning the document on the table, withdrawing the document from the table on termination of the scanning operation, and feeding a new document to the table. Such cycles of operation require to be performed in a number of times equal to the number of the documents multiplied by the desired number of the printed outputs to be produced for each of the documents. An extremely large amount of time is thus required for executing the scanner-moved scanning mode when the sorting mode is selected. This means that it will be scanning mode when the sorting mode is selected.
Thus, the document-moved scanning mode has advantages over the scanner-moved scanning mode and vice versa. The fact is however that most of the users of an image duplicating apparatus having the document-moved and scanner-moved modes would not be able to utilize the apparatus with adequate appreciation of the advantages of each mode. It is quite likely that the user of the apparatus selects the improper one of the modes for the duplicating operation under desired conditions and enables the apparatus to produce printed outputs of satisfactory quality in a short period of time.